Place the chicken thighs in a large resealable freezer bag, along with the salad dressing, garlic, onion chunks, Greek seasoning, mint, lemon juice, capers, and olives. Squeeze the ingredients together in the bag to mix, then remove excess air and seal the bag.
Thaw.
Preheat the oven to 400°.
Add the baby tomatoes to the sheet and stir to mix all the ingredients together.